U.S. patent application number 12/990954 was filed with the patent office on 2011-03-10 for urea-terminated polyurethane dispersants.
This patent application is currently assigned to E.I. DU PONT DE NEMOURS AND COMPANY. Invention is credited to Xiaoqing Li, Tyau-Jeen Lin, Patrick F. McIntyre.
Application Number | 20110060102 12/990954 |
Document ID | / |
Family ID | 40903969 |
Filed Date | 2011-03-10 |
United States Patent
Application |
20110060102 |
Kind Code |
A1 |
Li; Xiaoqing ; et
al. |
March 10, 2011 |
UREA-TERMINATED POLYURETHANE DISPERSANTS
Abstract
The present invention relates to urea terminated polyurethane
dispersants based on selected diols, aqueous dispersions of such
polyurethanes, the manufacture of the urea terminated polyurethane
dispersions, and inks containing pigments and/or disperse dyes
dispersed with these urea terminated polyurethane dispersants. The
urea termination can have nonionic hydrophilic substituents.
Inventors: |
Li; Xiaoqing; (Newark,
DE) ; Lin; Tyau-Jeen; (Chadds Ford, PA) ;
McIntyre; Patrick F.; (West Chester, PA) |
Assignee: |
E.I. DU PONT DE NEMOURS AND
COMPANY
Wilmington
DE
|
Family ID: |
40903969 |
Appl. No.: |
12/990954 |
Filed: |
May 22, 2009 |
PCT Filed: |
May 22, 2009 |
PCT NO: |
PCT/US09/44994 |
371 Date: |
November 4, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61128637 |
May 23, 2008 |
|
|
|
Current U.S.
Class: |
524/591 |
Current CPC
Class: |
C08G 18/6659 20130101;
C08G 18/12 20130101; C08G 18/755 20130101; C08G 18/0823 20130101;
C08G 18/3275 20130101; C08G 18/12 20130101; C08G 18/44 20130101;
C08G 18/3275 20130101; C08G 18/341 20130101; C08G 18/348 20130101;
C09D 11/326 20130101; C08G 18/4211 20130101 |
Class at
Publication: |
524/591 |
International
Class: |
C09D 11/10 20060101
C09D011/10; C08L 75/04 20060101 C08L075/04 |
Claims
1. An aqueous colorant dispersion comprising a colorant and a urea
terminated polyurethane ionic dispersant in an aqueous vehicle,
wherein: (a) the ionic dispersant is physically adsorbed to the
particle, (b) the polymeric ionic dispersant stably disperses the
pigment in the aqueous vehicle, (c) the average particle size of
the dispersion is less than about 300 nm, wherein the urea
terminated polyurethane dispersant comprises at least one compound
of the general Structure(I): ##STR00007## R.sub.1 is alkyl,
substituted alkyl, substituted alkyl/aryl from a diisocyanate,
R.sub.2 is alkyl, substituted/branched alkyl from a diol, R.sub.3
is alkyl, branched alkyl, or an isocyanate reactive group from an
amine terminating group, R.sub.4 is hydrogen, alkyl, branched
alkyl, or an isocyanate reactive group from the amine terminating
group; where the isocyanate reactive group is selected from the
group consisting of hydroxyl, carboxyl, mercapto, and amido; n is 2
to 30; and where R.sub.2 is at least one Z.sub.2 and at least one
Z.sub.1 or Z.sub.3, ##STR00008## m is greater than about 30 to
about 150, R.sub.5, R.sub.6 each is independently selected from the
group consisting of hydrogen, alkyl, substituted alkyl, and aryl;
where the R.sub.5 is the same or different for each substituted
methylene group where the R.sub.5 and R.sub.5 or R.sub.6 can be
joined to form a cyclic structure; Z.sub.2 is a diol substituted
with an ionic group; Z.sub.3 is selected from the group consisting
of polyester diols, polycarbonate diols, polyestercarbonate diols
and polyacrylate diols; wherein the urea content of the
urea-terminated polyurethane is at least 2 wt % of the polyurethane
and at most about 14 wt % of the polyurethane, and further wherein
the colorant is selected from pigments and disperse dyes or
combinations of pigments and disperse dyes.
2. The aqueous colorant dispersion of claim 1, where the urea
content of the urea terminated polyurethane is at least about 2.5
wt % and at most about 10.5 wt %.
3. The aqueous colorant dispersion of claim 1, where the ionic
content of the polyurethane is 10 to 190 milliequivalents per 100 g
of polyurethane.
4. The aqueous colorant dispersion of claim 1, where the ionic
content of the polyurethane is 20 to 140 milliequivalents per 100 g
of polyurethane.
5. The aqueous colorant dispersion of claim 1, where the ionic
content of the polyurethane is 20 to 90 milliequivalents per 100 g
of polyurethane.
6. The aqueous colorant dispersion of claim 1, where the colorant
to urea terminated polyurethane dispersant ratio is from about 0.5
to about 6 on a weight basis.
7. The aqueous colorant dispersion of claim 1, where R.sub.2
comprises at least Z.sub.2, at least one Z.sub.1 or Z.sub.3 and at
least one diol of the general Structure (IV) ##STR00009## p is
greater than or equal to 1, when p is 1, q greater than or equal to
3 to about 30, when p is 2 or greater, q greater than or equal to 3
to about 12; R.sub.7, R.sub.8 each is independently selected from
the group consisting of hydrogen, alkyl, substituted alkyl, and
aryl; where the R.sub.7 is the same or different for each
substituted methylene group where the R.sub.7 and R.sub.7 or
R.sub.8 can be joined to form a cyclic structure.
8. An aqueous colored ink jet ink comprising the aqueous colorant
dispersion of claim 1, having from about 0.1 to about 10 wt %
pigment based on the total weight of the ink, a weight ratio of
colorant to urea terminated polyurethane dispersant of from about
0.5 to about 6, a surface tension in the range of about 20 dyne/cm
to about 70 dyne/cm at 25.degree. C., and a viscosity of lower than
about 30 cP at 25.degree. C.
9. An inkjet ink composition comprising an aqueous vehicle and
colorant particles stabilized by an urea terminated polyurethane
dispersant in an aqueous vehicle wherein the urea terminated
polyurethane dispersant comprises at least one compound of the
general Structure (I): ##STR00010## R.sub.1 is alkyl, substituted
alkyl, substituted alkyl/aryl from a diisocyanate, R.sub.2 is
alkyl, substituted/branched alkyl from a diol, R.sub.3 is alkyl,
branched alkyl, or an isocyanate reactive group from an amine
terminating group, R.sub.4 is hydrogen, alkyl, branched alkyl, or
an isocyanate reactive group from the amine terminating group;
where the isocyanate reactive group is selected from the group
consisting of hydroxyl, carboxyl, mercapto, and amido; n is 2 to
30; and where R.sub.2 is at least one Z.sub.2 and at least one
Z.sub.1 or Z.sub.3 ##STR00011## m is greater than about 30 to about
150, R.sub.5, R.sub.6 each is independently selected from the group
consisting of hydrogen, alkyl, substituted alkyl, and aryl; where
the R.sub.5 is the same or different for each substituted methylene
group where the R.sub.5 and R.sub.5 or R.sub.6 can be joined to
form a cyclic structure; Z.sub.2 is a diol substituted with an
ionic group; Z.sub.3 is selected from the group consisting of
polyester diols, polycarbonate diols, polyestercarbonate diols and
polyacrylate diols; and wherein the urea content of the
urea-terminated polyurethane is at least 2 wt % of the polyurethane
and at most about 14 wt % of the polyurethane,
10. A process for making a dispersed pigment comprising the step of
mixing the pigment and a urea terminated polyurethane dispersant in
an aqueous carrier medium, then dispersing or deflocculating the
pigment.
11. The method of claim 9, wherein the dispersing is accomplished
in a process selected from the group consisting of 2-roll milling,
media milling, and by passing the mixture through a plurality of
nozzles within a liquid jet interaction chamber at a liquid
pressure of at least 5,000 psi.
12. A process for making a dispersed pigment comprising the steps
of a) preparing a urea terminated polyurethane dispersant and then
mixing the pigment and the urea terminated polyurethane dispersant
in an aqueous carrier medium, then dispersing or deflocculating the
pigment where the urea terminated polyurethane (Structure I) is
prepared by (a) providing reactants comprising (i) at least one
diol Z.sub.1 or Z.sub.3 ii) at least one polyisocyanate component
comprising a diisocyanate, and (iii) at least one hydrophilic
reactant comprising at least one isocyanate reactive ingredient
containing an ionic group, Z.sub.2; (b) contacting (i), (ii) and
(iii) in the presence of a water-miscible organic solvent to form
an isocyanate-functional polyurethane prepolymer; (c) adding water
to form an aqueous dispersion; and (d) prior to, concurrently with
or subsequent to step (c), chain-terminating the
isocyanate-functional prepolymer with a primary or secondary
amine.
13. The particle of claim 1, where the particle is a pigment or
disperse dye.
14. The dispersion of claim 1, where the pigment to urea terminated
polyurethane dispersant ratio is from about 0.5 to about 6 on a
weight basis.
15. The dispersion of claim 1 where the pigment to urea terminated
polyurethane dispersant ratio is from about 0.75 to about 4 on a
weight basis.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority under 35 U.S.C. .sctn.119
from U.S. Provisional Application Ser. No. 61/128,637, filed May
23, 2008.
FIELD OF THE INVENTION
[0002] The present invention relates to urea-terminated
polyurethane dispersants based on certain diols. These polyurethane
dispersants are effective for dispersion of particles, especially
pigment particles. Pigments dispersed with the polyurethane
dispersants can be used in ink jet inks.
BACKGROUND OF THE INVENTION
[0003] Disclosed herein are novel polyurethane dispersants and
stable aqueous particle dispersions made there from, especially
pigment dispersions, a process of making the pigment dispersions
and use thereof in ink jet inks.
[0004] Polyurethane polymers can be manufactured by a variety of
well-known methods, but are often prepared by first making an
isocyanate-terminated "prepolymer" from polyols, polyisocyanates
and other optional compounds, then chain-extending and/or
chain-terminating this prepolymer to obtain a polymer possessing an
appropriate molecular weight and other properties for a desired end
use. Tri- and higher-functional starting components can be utilized
to impart some level of branching and/or crosslinking to the
polymer structure (as opposed to simple chain extension).
[0005] Polyurethane dispersions that are used as pigment
dispersants have been described in U.S. Pat. No. 6,133,890. These
polyurethanes are prepared with an excess of isocyanate reactive
group and are limited to the presence of polyalkylene oxide
components. Aqueous polyurethane dispersants have found limited use
as dispersants for pigments and the like.
[0006] None of the above publications disclose polyurethane
dispersions used as pigment dispersants that are derived from water
dispersible urea terminated polyurethanes based on certain
diols.
[0007] There is still a need for polyurethane dispersions which are
stable and provide improved performance properties when utilized in
desired end uses, such as when utilized as a pigment dispersant in
ink jet ink applications. These polyurethanes, as described herein,
can be used as dispersants for pigments, especially pigments for
inkjet inks, and posses a unique balance of properties especially
desirable for ink jet ink applications.
SUMMARY OF THE INVENTION
[0008] The use of polymeric conventional dispersants is well
established as a means to make stable dispersants of particles,
especially pigment particles. In general, these conventional
dispersants have, at least, modest water solubility and this water
solubility is used as a guide to predicting dispersion stability.
These dispersants are most often based on acrylate/acrylic
compounds. During diligent searching for new, improved polymeric
dispersants, a new class of dispersants has been found that are
based on urea terminated polyurethanes, where the predominant
isocyanate reactive group is a hydroxyl derived from select diols.
The ionic content in these dispersants come from isocyanate or
isocyanate-reactive components that have ionic substitution.
[0009] Accordingly, there are provided herein dispersants, namely
urea terminated polyurethane dispersants, that lead to stable
aqueous dispersions, stable aqueous dispersions containing these
polyurethane dispersants, methods of making urea terminated
polyurethane dispersants, inks based on urea terminated
polyurethane dispersants, inks sets comprising at least one ink
based on an urea terminated polyurethane dispersants, and methods
of ink jet printing that use the inks based on urea terminated
polyurethane dispersants.
[0010] An embodiment provides an aqueous particle dispersion
comprising a particle, preferably a colorant particle, and an urea
terminated polyurethane ionic dispersant in an aqueous vehicle,
wherein:
[0011] (a) the ionic dispersant is physically adsorbed to the
particle,
[0012] (b) the polymeric ionic dispersant stably disperses the
pigment in the aqueous vehicle,
[0013] (c) the average particle size of the dispersion is less than
about 300 nm, and
wherein the urea terminated polyurethane ionic dispersant comprises
at least one compound of the general Structure (I):
##STR00001##
R.sub.1 is alkyl, substituted alkyl, substituted alkyl/aryl from a
diisocyanate, R.sub.2 is alkyl, substituted/branched alkyl from a
diol, R.sub.3 is alkyl, branched alkyl, or a isocyanate reactive
group from an amine terminating group, R.sub.4 is hydrogen, alkyl,
branched alkyl, or a isocyanate reactive group from the amine
terminating group; where the isocyanate reactive group is selected
from the group consisting of hydroxyl, carboxyl, mercapto, and
amido; n is 2 to 30; and where R.sub.2 is at least one Z.sub.2 and
at least one Z.sub.1 or Z.sub.3
##STR00002##
m greater than about 30 to about 150, R.sub.5, R.sub.6 each is
independently hydrogen, alkyl, substituted alkyl, and aryl; where
the R.sub.5 is the same or different for each substituted methylene
group where the R.sub.5 and R.sub.5 or R.sub.6 can be joined to
form a cyclic structure; Z.sub.2 is a diol substituted with an
ionic group; Z.sub.3 is selected from the group consisting of
polyester diols, polycarbonate diols, polyestercarbonate diols and
polyacrylate diols; wherein the urea content of the urea-terminated
polyurethane of general Structure (I) is at least 2 wt % of the
polyurethane and at most about 14 wt % of the polyurethane, and
preferably wherein the particle is a colorant and the colorant is
selected from pigments and disperse dyes or combinations of
pigments and disperse dye.
[0014] A further embodiment wherein the aqueous polyurethane
dispersant composition comprises an urea-terminated polyurethane as
generally set forth above, wherein the polyurethane contains a
sufficient amount of ionic functionality in order to render the
polyurethane dispersed particles dispersible in the continuous
phase of the dispersion.
[0015] Within yet another embodiment provides a method of preparing
a stable dispersion of particles such as pharmaceuticals and
colorants. The first step in the preparation is preparing an
aqueous dispersion of an aqueous urea terminated polyurethane
composition comprising the steps:
[0016] (a) providing reactants comprising (i) at least one diol
Z.sub.3 or Z.sub.1 as defined above ii) at least one polyisocyanate
component comprising a diisocyanate, and (iii) at least one
hydrophilic reactant comprising at least one isocyanate reactive
ingredient containing an ionic group, Z.sub.2 as defined above;
[0017] (b) contacting (i), (ii) and (iii) in the presence of a
water-miscible organic solvent to form an isocyanate-functional
polyurethane prepolymer;
[0018] (c) adding water to form an aqueous dispersion; and
[0019] (d) prior to, concurrently with or subsequent to step (c),
chain-terminating the isocyanate-functional prepolymer with a
primary or secondary amine.
[0020] The diol, diisocyanate and hydrophilic reactant may be added
together in any order.
[0021] The chain terminating amine is typically added prior to
addition of water in an amount to react with substantially any
remaining isocyanate functionality. The chain terminating amine is
optionally a nonionic secondary amine.
[0022] If the hydrophilic reactant contains ionizable groups then,
at the time of addition of water (step (c)), the ionizable groups
must be ionized by adding acid or base (depending on the type of
ionizable group) in an amount such that the polyurethane can be
stably dispersed.
[0023] Preferably, at some point during the reaction (generally
after addition of water and after chain extension), the organic
solvent is substantially removed under vacuum to produce an
essentially solvent-free dispersion.
[0024] After the polyurethane dispersion is prepared it is used in
the dispersion of particles by known dispersion techniques.
[0025] Another embodiment provides an aqueous colored ink jet ink
comprising an aqueous colorant dispersion as described above,
having from about 0.1 to about 10 wt % pigment based on the total
weight of the ink, a weight ratio of colorant to polyurethane
dispersant of from about 0.5 to about 6, a surface tension in the
range of about 20 dyne/cm to about 70 dyne/cm at 25.degree. C., and
a viscosity of lower than about 30 cP at 25.degree. C.
[0026] Another embodiment provides an ink set comprising at least
one cyan ink, at least one magenta ink and at least one yellow ink,
wherein at least one of the inks is an aqueous pigmented ink jet
ink as set forth above and described in further detail below.
[0027] The continuous phase of the aqueous dispersion, in addition
to water, may further comprise water-miscible organic solvent.
Optionally the level of organic solvent is from about 0 wt % to
about 30 wt %, based on the weight of the continuous phase.
[0028] These polyurethane dispersants are effective dispersants for
pigments, pharmaceuticals and other dispersions of small particles.
The polyurethanes dispersions shown is Structure (I) can also be
added to the aqueous ink as an additive.
[0029] These and other features and advantages of the present
invention will be more readily understood by those of ordinary
skill in the art from a reading of the following Detailed
Description. Certain features of the invention which are, for
clarity, described above and below as a separate embodiments, may
also be provided in combination in a single embodiment. Conversely,
various features of the invention that are described in the context
of a single embodiment, may also be provided separately or in any
subcombination.
DETAILED DESCRIPTION
[0030] Unless otherwise stated or defined, all technical and
scientific terms used herein have commonly understood meanings by
one of ordinary skill in the art to which this invention
pertains.
[0031] Unless stated otherwise, all percentages, parts, ratios,
etc., are by weight.
[0032] When an amount, concentration, or other value or parameter
is given as either a range, preferred range or a list of upper
preferable values and lower preferable values, this is to be
understood as specifically disclosing all ranges formed from any
pair of any upper range limit or preferred value and any lower
range limit or preferred value, regardless of whether ranges are
separately disclosed. Where a range of numerical values is recited
herein, unless otherwise stated, the range is intended to include
the endpoints thereof, and all integers and fractions within the
range.
[0033] When the term "about" is used in describing a value or an
end-point of a range, the disclosure should be understood to
include the specific value or end-point referred to.
[0034] As used herein, the dispersions produced with the
polyurethane described above can be utilized to disperse particles,
especially pigments for inkjet inks. These inks can be printed on
all normally used inkjet substrates including textile
substrates.
[0035] As used herein, the term "dispersion" means a two phase
system where one phase consists of finely divided particles (often
in the colloidal size range) distributed throughout a bulk
substance, of the particles being the dispersed or internal phase
and the bulk substance that continuous or external phase.
[0036] As used herein, the term "dispersant" means a surface active
agent added to a suspending medium to promote uniform and maximum
separation of extremely fine solid particles often of colloidal
size. For pigments dispersants are most often polymeric
dispersants. The polyurethane dispersants described herein are in
fact dispersions themselves.
[0037] As used herein, the term "OD" means optical density.
[0038] As used herein, the term "aqueous vehicle" refers to water
or a mixture of water and at least one water-soluble organic
solvent (co-solvent).
[0039] As used herein, the term "ionizable groups," means
potentially ionic groups.
[0040] As used herein, the term "substantially" means being of
considerable degree, almost all.
[0041] As used herein, the term "Mn" means number average molecular
weight.
[0042] As used herein, the term "Mw" means weight average molecular
weight.
[0043] As used herein, the term "Pd" means the polydispersity which
is the weight average molecular weight divided by the number
average molecular weight.
[0044] As used herein, the term "d50" means the particle size at
which 50% of the particles are smaller; "d95" means the particle
size at which 95% of the particles are smaller.
[0045] As used herein, the term "colorfastness" is described as
"the resistance of a material to change in any of its color
characteristics. This term is especially useful for describing
printed textiles.
[0046] As used herein, the term "washfastness" is described as the
resistance to loss of the printed color/image after washing a
printed textile.
[0047] As used herein, the term "Crock" is described as the
resistance to rubbing off of a printed color/image after washing a
printed textile.
[0048] As used herein, the term "cP" means centipoise, a viscosity
unit.
[0049] As used herein, the term "prepolymer" means the polymer that
is an intermediate in a polymerization process, and can be
considered a polymer.
[0050] As used herein, the term "AN" means acid number, mg KOH/gram
of solid polymer.
[0051] As used herein, the term "neutralizing agents" means to
embrace all types of agents that are useful for converting
ionizable groups to the more hydrophilic ionic (salt) groups.
[0052] As used herein, the term "PUD" means the polyurethanes
dispersions described herein.
[0053] As used herein, the term "BMEA" means bis(methoxyethyl)
amine.
[0054] As used herein, the term "DBTDL" means dibutyltin
dilaurate.
[0055] As used herein, the term "DMEA" means
dimethylethanolamine.
[0056] As used herein, the term "DMIPA" means
dimethylisopropylamine.
[0057] As used herein, the term "DEA" means diethanolamine
[0058] As used herein, the term "DMPA" means dimethylol propionic
acid.
[0059] As used herein, the term "DMBA" means dimethylol butyric
acid.
[0060] As used herein, the term "EDA" means ethylenediamine.
[0061] As used herein, the term "EDTA" means
ethylenediaminetetraacetic acid.
[0062] As used herein, the term "HDI" means 1,6-hexamethylene
diisocyanate.
[0063] As used herein, the term "GPC" means gel permeation
chromatography.
[0064] As used herein, the term "IPDI" means isophorone
diisocyanate.
[0065] As used herein, the term "TMDI" means trimethylhexamethylene
diisocyanate.
[0066] As used herein, the term "TMXDI" means m-tetramethylene
xylylene diisocyanate.
[0067] As used herein, the term "ETEGMA//BZMA//MAA" means the block
copolymer of ethoxytriethyleneglycol methacrylate,
benzylmethacrylate and methacrylic acid.
[0068] As used herein the term T650 means TERATHANE 650, see
below.
[0069] As used herein, the term "PO3G" means 1,3-propanediol.
[0070] As used herein, the term"DMPA" means dimethylol propionic
acid
[0071] As used herein, the term "NMP" means n-Methyl
pyrolidone.
[0072] As used herein, the term "TEA" means triethylamine.
[0073] As used herein, the term "TEOA" means triethanolamine.
[0074] As used herein, the term "TETA" means
triethylenetetramine.
[0075] As used herein, the term "THF" means tetrahydrofuran.
[0076] As used herein, the term "Tetraglyme" means Tetraethylene
glycol dimethyl ether.
[0077] TERATHANE 650 is a 650 molecular weight, polytetramethylene
ether glycol (PTMEG) from purchased from Invista, Wichita,
Kans.
[0078] TERATHANE 250 is a 250 molecular weight, polytetramethylene
ether glycol.
[0079] Pripol 2033 is a hydrocarbon diol from Uniqema,
Netherland
[0080] Unless otherwise noted, the above chemicals were obtained
from Aldrich (Milwaukee, Wis.) or other similar suppliers of
laboratory chemicals.
Urea-Terminated Polyurethane Dispersants
[0081] Polyurethane polymers are, for the purposes of the present
disclosure, polymers wherein the polymer backbone contains urethane
linkage derived from the reaction of an isocyanate group (from,
e.g., a di- or higher-functional monomeric, oligomeric and/or
polymeric polyisocyanate) with a hydroxyl group (from, e.g., a di-
or higher-functional monomeric, oligomeric and/or polymeric
polyol). Such polymers may, in addition to the urethane linkage,
also contain other isocyanate-derived linkages such as urea, as
well as other types of linkages present in the polyisocyanate
components and/or polyol components (such as, for example, ester
and ether linkage).
[0082] The urea terminated polyurethane dispersant comprises at
least one compound of the general Structure (I):
##STR00003##
R.sub.1 is alkyl, substituted alkyl, substituted alkyl/aryl from a
diisocyanate, R.sub.2 is alkyl, substituted/branched alkyl from a
diol, R.sub.3 is alkyl, branched alkyl, or a isocyanate reactive
group from an amine terminating group, R.sub.4 is hydrogen, alkyl,
branched alkyl, or a isocyanate reactive group from the amine
terminating group; where the isocyanate reactive group is selected
from the group consisting of hydroxyl, carboxyl, mercapto, and
amido; n is 2 to 30; and where R.sub.2 is at least one Z.sub.2 and
at least one Z.sub.1 or Z.sub.3,
##STR00004##
m greater than about 30 to about 150, R.sub.5, R.sub.6 each is
independently selected from the group consisting of hydrogen,
alkyl, substituted alkyl, and aryl; where the R.sub.5 is the same
or different for each substituted methylene group where the R.sub.5
and R.sub.5 or R.sub.6 can be joined to form a cyclic structure;
Z.sub.2 is a diol substituted with an ionic group; Z.sub.3 is
selected from the group consisting of polyester diols,
polycarbonate diols, polyestercarbonate diols and polyacrylate
diols;
[0083] wherein a weight fraction of a urea terminating component
part of the polyurethane is at least 2 wt % to the urethane
resin,
[0084] and further preferably wherein the particle is a colorant
and the colorant is selected from pigments and disperse dyes or
combinations of pigments and disperse dye.
[0085] Structure (I) denotes the urea terminated polyurethane and
Structure (II) denotes a hydrocarbon diol which can be used as a
component of the urea terminated polyurethane.
[0086] The invention also relates to a method of preparing a stable
dispersion of particles such as pharmaceuticals and colorants. The
first step in the preparation is preparing an aqueous dispersion of
an aqueous urea terminated polyurethane composition comprising the
steps:
[0087] (a) providing reactants comprising (i) at least one diol
Z.sub.3 or Z.sub.1 as defined above ii) at least one polyisocyanate
component comprising a diisocyanate, and (iii) at least one
hydrophilic reactant comprising at least one isocyanate reactive
ingredient containing an ionic group, Z.sub.2, as defined
above;
[0088] (b) contacting (i), (ii) and (iii) in the presence of a
water-miscible organic solvent to form an isocyanate-functional
polyurethane prepolymer;
[0089] (c) adding water to form an aqueous dispersion; and
[0090] (d) prior to, concurrently with or subsequent to step (c),
chain-terminating the isocyanate-functional prepolymer with a
primary or secondary amine
[0091] The diol, diisocyanate and hydrophilic reactant may be added
together in any order. The total moles of isocyanate groups exceed
the moles of isocyanate reactive groups prior to the addition of
the chain terminating agent.
[0092] The chain terminating amine is typically added prior to
addition of water in an amount to react with substantially any
remaining isocyanate functionality. The chain terminating amine is
optionally a nonionic secondary amine.
[0093] If the hydrophilic reactant contains ionizable groups then,
at the time of addition of water (step (c)), the ionizable groups
must be ionized by adding acid or base (depending on the type of
ionizable group) in an amount such that the polyurethane can be
stably dispersed.
[0094] Specifically, at some point during the reaction (generally
after addition of water and after chain extension), the organic
solvent is substantially removed under vacuum to produce an
essentially solvent-free dispersion.
[0095] The key features of the polyurethane dispersant are the diol
selected from hydrocarbon diols (Structure II), polyester diols,
polycarbonate diols, polyestercarbonate diols and polyacrylate
diols; and the monofunctional amine which results in the urea
termination. Without being bound by theory, these polyurethane
dispersants perform better as dispersants for pigments etc. Also,
the diol/urea termination combination seems to produce a relatively
pure polyurethane that does not have contamination and/or extensive
crosslinking that can lead to poorer performance dispersing
pigments and the like.
[0096] Hydrocarbon diols of Structure (II), provide polyurethanes
with significant areas of hydrophobic groups which can be effective
in dispersing pigments. Often these materials are derived from
polyolefins and these are available from Shell as KRATON LIQUID L
and Mitsubishi Chemical as POLYTAIL H. While not being bound by
theory these areas of hydrophobic groups may be effective as the
part of the dispersant that is associated with the pigment
surfaces.
[0097] Polyester diols, polycarbonate diols, polyestercarbonate
diols and polyacrylate diols are all diols that provide formulation
latitude for the polyurethane.
[0098] Suitable polyester polyols include reaction products of
polyhydric; dihydric alcohols to which trihydric alcohols may
optionally be added, and polybasic (preferably dibasic) carboxylic
acids. Trihydic alcohols are limited to at most about 2 weight such
that some branching can occur but no significant crosslinking would
occur, and may be used in cases in which modest branching of the
NCO prepolymer or polyurethane is desired. Instead of these
polycarboxylic acids, the corresponding carboxylic acid anhydrides
or polycarboxylic acid esters of lower alcohols or mixtures thereof
may be used for preparing the polyesters.
[0099] The polycarboxylic acids may be aliphatic, cycloaliphatic,
aromatic and/or heterocyclic or mixtures thereof and they may be
substituted, for example, by halogen atoms, and/or unsaturated. The
following are mentioned as examples: succinic acid; adipic acid;
suberic acid; azelaic acid; sebacic acid; 1,12-dodecyldioic acid;
phthalic acid; isophthalic acid; trimellitic acid; phthalic acid
anhydride; tetrahydrophthalic acid anhydride; hexahydrophthalic
acid anhydride; tetrachlorophthalic acid anhydride; endomethylene
tetrahydrophthalic acid anhydride; glutaric acid anhydride; maleic
acid; maleic acid anhydride; fumaric acid; dimeric and trimeric
fatty acids such as oleic acid, which may be mixed with monomeric
fatty acids; dimethyl terephthalates and bis-glycol
terephthalate.
[0100] Preferable polyester diols can be blending with hydroxyl
terminated poly(butylene adipate), poly(butylene succinate),
poly(ethylene adipate), poly(1,2-propylene adipate),
poly(trimethylene adipate), poly(trimethylene succinate),
polylactic acid ester diol and polycaprolactone diol. Other
hydroxyl terminated polyester diols are copolyethers comprising
repeat units derived from a diol and a sulfonated dicarboxylic acid
and prepared as described in U.S. Pat. No. 6,316,586.
[0101] Polycarbonates containing hydroxyl groups include those
known, per se, such as the products obtained from the reaction of
diols such as propanediol-(1,3), butanediol-(1,4) and/or
hexanediol-(1,6), diethylene glycol, triethylene glycol or
tetraethylene glycol, higher polyether diols with phosgene,
diarylcarbonates such as diphenylcarbonate, dialkylcarbonates such
as diethylcarbonate or with cyclic carbonates such as ethylene or
propylene carbonate. Also suitable are polyester carbonates
obtained from the above-mentioned polyesters or polylactones with
phosgene, diaryl carbonates, dialkyl carbonates or cyclic
carbonates.
[0102] Polycarbonate diols for blending are optionally selected
from the group consisting of polyethylene carbonate diol,
polytrimethylene carbonate diol, polybutylene carbonate diol and
polyhexylene carbonate.
[0103] Poly(meth)acrylates containing hydroxyl groups include those
common in the art of addition polymerization such as cationic,
anionic and radical polymerization and the like. Examples are
alpha-omega diols. An example of these type of diols are those
which are prepared by a "living" or "control" or chain transfer
polymerization processes which enables the placement of one
hydroxyl group at or near the termini of the polymer. U.S. Pat. No.
6,248,839 and U.S. Pat. No. 5,990,245 (have examples of protocol
for making terminal diols. Other di-NCO reactive poly(meth)acrylate
terminal polymers can be used. An example would be end groups other
than hydroxyl such as amino or thiol, and may also include mixed
end groups with hydroxyl.
Chain Termination Reactant
[0104] The terminating agent is a primary or secondary monoamine
which is added to make the urea termination. In Structure (I) the
terminating agent is shown as R.sub.3(R.sub.4)N-substituent on the
polyurethane. An optional substitution pattern for R.sub.3 and
R.sub.4 are alkyl, a non-isocyanate reactive substituted/branched
alkyl from an amine group, isocyanate reactive substituted/branched
alkyl where an isocyanate reactive group is selected from hydroxyl,
carboxyl, mercapto, amide and other ones which has less isocyanate
reactivity than primary or secondary amine.
[0105] The amount of chain terminator employed should be
approximately equivalent to the free isocyanate groups in the
prepolymer. The ratio of active hydrogens from amine in the chain
terminator to isocyanate groups in the prepolymer is in the range
from about 1.0:1 to about 1.2:1, more specifically from about
1.0:1.1 to about 1.1:1, and still more optionally from about
1.0:1.05 to about 1.1:1, on an equivalent basis. Although any
isocyanate groups that are not terminated with an amine can react
with other isocyanate reactive functional group and/or water the
ratios of chain termination to isocyanate group is chosen to assure
a urea termination. Amine termination of the polyurethane is
avoided by the choice and amount of chain terminating agent leading
to a urea terminated polyurethane. This results in better molecular
weight control and better properties when uses as a particle
dispersant and when freely added to formulations.
[0106] Any primary or secondary monoamines substituted with less
isocyanate reactive groups may be used as chain terminators.
Especially useful are aliphatic primary or secondary monoamines are
preferred. Less isocyanate reactive groups could be hydroxyl,
carboxyl, amide and mercapto. Example of monoamines useful as chain
terminators include but are not restricted to diethanolamine,
monoethanolamine, 3-amino-1-propanol, isopropanolamine,
N-ethylethanolamine, diisopropanolamine, 6-aminocaproic acid,
8-aminocaprylic acid, and 3-aminoadipic acid. An optional
isocyanate reactive chain terminator is diethanolamine. The
diethanolamine is part of a optional class of urea terminating
reactant where the substituents are hydroxyl functionalities which
could provide improved pigment wetting.
[0107] The urea content in percent of the polyurethane is
determined by dividing the mass of chain terminator by the sum of
the other polyurethane components including the chain terminating
agent. The urea content will be from about 2 wt % to about 14 wt %.
The urea content will be optionally from about 2.5 wt % to about
10.5 wt %. The 0.75 wt % occurs when the diols used are large, for
instance M.sub.n is greater than about 4000 and/or the molecular
weight of the isocyanate is high.
Polyisocyanate Component
[0108] Suitable polyisocyanates are those that contain either
aromatic, cycloaliphatic or aliphatic groups bound to the
isocyanate groups. Mixtures of these compounds may also be used. If
aromatic isocyanates are used, cycloaliphatic or aliphatic
isocyanates can be present as well. R.sub.1 can be optionally
substituted with aliphatic groups.
[0109] Diisocyanates are preferred, and any diisocyanate useful in
preparing polyurethanes and/or polyurethane-ureas from polyether
glycols, diisocyanates and diols or amine can be used in this
invention.
[0110] Examples of suitable diisocyanates include, but are not
limited to, 2,4-toluene diisocyanate (TDI); 2,6-toluene
diisocyanate; trimethyl hexamethylene diisocyanate (TMDI);
4,4'-diphenylmethane diisocyanate (MDI); 4,4'-dicyclohexylmethane
diisocyanate (H.sub.12MDI); 3,3'-dimethyl-4,4'-biphenyl
diisocyanate (TODD; Dodecane diisocyanate (C.sub.12DI);
m-tetramethylene xylylene diisocyanate (TMXDI); 1,4-benzene
diisocyanate; trans-cyclohexane-1,4-diisocyanate; 1,5-naphthalene
diisocyanate (NDI); 1,6-hexamethylene diisocyanate (HDI);
4,6-xylyene diisocyanate; isophorone diisocyanate (IPDI); and
combinations thereof.
[0111] Small amounts, optionally less than about 3 wt % based on
the weight of the diisocyanate, of monoisocyanates or
polyisocyanates can be used in mixture with the diisocyanate.
Examples of useful monoisocyanates include alkyl isocyanates such
as octadecyl isocyanate and aryl isocyanates such as phenyl
isocyanate. Example of a polyisocyanate are triisocyanatotoluene
HDI trimer (Desmodur 3300), and polymeric MDI (Mondur MR and
MRS).
Ionic Reactants
[0112] The hydrophilic reactant contains ionic and/or ionizable
groups (potentially ionic groups). The ionic reactants contain one
or two, isocyanate reactive groups, as well as at least one ionic
or ionizable group. In the structural description of the urea
terminated polyether polyurethane described herein the reactant
containing the ionic group is designated as Z.sub.2. In the context
of this disclosure, the term "isocyanate reactive groups" is taken
to include groups well known to those of ordinary skill in the
relevant art to react with isocyanates, and specifically hydroxyl,
primary amino and secondary amino groups.
[0113] Examples of ionic dispersing groups include carboxylate
groups (--COOM), phosphate groups (--OPO.sub.3M.sub.2), phosphonate
groups (--PO.sub.3M.sub.2), sulfonate groups (--SO.sub.3 M),
quaternary ammonium groups (--NR.sub.3Y, wherein Y is a monovalent
anion such as chlorine or hydroxyl), or any other effective ionic
group. M is a cation such as a monovalent metal ion (e.g.,
Na.sup.+, K.sup.+, Li.sup.+, etc.), H.sup.+, NR.sub.4.sup.+, and
each R can be independently an alkyl, aralkyl, aryl, or hydrogen.
These ionic dispersing groups are typically located pendant from
the polyurethane backbone.
[0114] The ionizable groups in general correspond to the ionic
groups, except they are in the acid (such as carboxyl --COOH) or
base (such as primary, secondary or tertiary amine --NH.sub.2,
--NRH, or --NR.sub.2) form. The ionizable groups are such that they
are readily converted to their ionic form during the
dispersion/polymer preparation process as discussed below.
[0115] The ionic or potentially ionic groups are chemically
incorporated into the polyurethane in an amount to provide an ionic
content (with neutralization as needed) sufficient to render the
polyurethane dispersible in the aqueous medium of the dispersion.
Typical ionic content will range from about 10 up to about 190
milliequivalents (meq), optionally from about 20 to about 140 meq.,
per 100 g of polyurethane, and additionally less than about 90 meq
per 100 g of urea terminated polyurethane.
[0116] With respect to compounds which contain isocyanate reactive
groups and ionic or potentially ionic groups, the isocyanate
reactive groups are typically amino and hydroxyl groups. The
potentially ionic groups or their corresponding ionic groups may be
cationic or anionic, although the anionic groups are preferred.
Specific examples of anionic groups include carboxylate and
sulfonate groups. Examples of cationic groups include quaternary
ammonium groups and sulfonium groups.
[0117] In the case of anionic group substitution, the groups can be
carboxylic acid groups, carboxylate groups, sulphonic acid groups,
sulphonate groups, phosphoric acid groups and phosphonate groups,
The acid salts are formed by neutralizing the corresponding acid
groups either prior to, during or after formation of the NCO
prepolymer.
[0118] Suitable compounds for incorporating carboxyl groups are
described in U.S. Pat. No. 3,479,310, U.S. Pat. No. 4,108,814 and
U.S. Pat. No. 4,408,008. Examples of carboxylic group-containing
compounds are the hydroxy-carboxylic acids corresponding to the
formula (HO).sub.xQ(COOH).sub.y wherein Q represents a straight or
branched, hydrocarbon radical containing 1 to 12 carbon atoms, x is
1 or 2), and y is 1 to 3. Examples of these hydroxy-carboxylic
acids include citric acid, tartaric acid and hydroxypivalic acid.
Optional dihydroxy alkanoic acids include the
alpha,alpha-dimethylol alkanoic acids represented by the Structure
(IV):
##STR00005##
wherein Q' is hydrogen or an alkyl group containing 1 to 8 carbon
atoms. (The .alpha.,.alpha.-dimethylol alkanoic acids represented
by the structural formula R.sup.7C--(CH.sub.2OH).sub.2--COOH,
wherein R.sup.7 is hydrogen or an alkyl group containing 1 to 8
carbon atoms. Examples of these ionizable diols include but are not
limited to dimethylolacetic acid, 2,2'-dimethylolbutanoic acid,
2,2'-dimethylolpropionic acid ((DMPA), i.e., wherein Q' is methyl
in the above formula), and 2,2'-dimethylolbutyric acid. Suitable
carboxylates also include
H.sub.2N--(CH.sub.2).sub.4--CH(CO.sub.2H)--NH.sub.2, and
H.sub.2N--CH.sub.2--CH.sub.2--NH--CH.sub.2--CH.sub.2--CO.sub.2Na
[0119] The optional sulfonate groups for incorporation into the
polyurethanes are the diol sulfonates as disclosed in U.S. Pat. No.
4,108,814. Suitable diol sulfonate compounds also include hydroxyl
terminated copolyethers comprising repeat units derived from the
reaction of a diol and a sulfonated dicarboxylic acid. The specific
sulfonated dicarboxylic acid/diol combination is
5-sulfo-isophthalic acid, and 1,3-propanediol. Other suitable
sulfonates also include
H.sub.2N--CH.sub.2--CH.sub.2--NH--(CH.sub.2).sub.r--SO.sub.3Na,
where r is 2 or 3.
[0120] When the ionic stabilizing groups are acids, the acid groups
are incorporated in an amount sufficient to provide an acid group
content for the urea-terminated polyurethane, known by those
skilled in the art as acid number (mg KOH per gram solid polymer),
of at least about 6, optionally at least about 10 milligrams KOH
per 1.0 gram of polyurethane and even more specifically 20
milligrams KOH per 1.0 gram of polyurethane, The upper limit for
the acid number (AN) is about 120, and optionally about 90.
[0121] Within the context of this disclosure, the term
"neutralizing agents" is meant to embrace all types of agents which
are useful for converting potentially ionic or ionizable groups to
ionic groups. Accordingly, this term also embraces quaternizing
agents and alkylating agents.
[0122] When amines are used as the neutralizing agent, the chain
terminating reaction producing the urea termination is preferably
completed prior to addition of the neutralizing agent that can also
behave as an isocyanate reactive group.
[0123] In order to convert the anionic groups to the salt form
either before, during or after their incorporation into the
prepolymers, either volatile or nonvolatile basic materials may be
used to form the counterions of the anionic groups. Volatile bases
are those wherein at least about 90% of the base used to form the
counterion of the anionic group volatilizes under the conditions
used to remove water from the aqueous polyurethane dispersions.
Nonvolatile basic materials are those wherein at least about 90% of
the base does not volatilize under the conditions used to remove
water from the aqueous polyurethane dispersions.
[0124] Suitable volatile basic organic compounds for neutralizing
the potential anionic groups are the primary, secondary or tertiary
amines Examples of these amines are trimethyl amine, triethyl
amine, triisopropyl amine, tributyl amine, N,N-dimethyl-cyclohexyl
amine, N,N-dimethylstearyl amine, N,N-dimethylaniline,
N-methylmorpholine, N-ethylmorpholine, N-methylpiperazine,
N-methylpyrrolidine, N-methylpiperidine, N,N-dimethyl-ethanol
amine, N,N-diethyl-ethanol amine, triethanolamine,
N-methyldiethanol amine, dimethylaminopropanol,
2-methoxyethyidimethyl amine, N-hydroxyethylpiperazine,
2-(2-dimethylaminoethoxy)-ethanol and
5-diethylamino-2-pentanone.
[0125] Suitable nonvolatile basic materials include monovalent
metals, especially the alkali metals, lithium, sodium and
potassium; with the basic counterions, hydroxides, carbonates or
bicarbonates.
[0126] When the potential cationic or anionic groups of the
polyurethane are neutralized, they provide hydrophilicity to the
polymer and better enable it to be stably dispersed in water. The
neutralization steps may be conducted (1) prior to polyurethane
formation by treating the component containing the potentially
ionic group(s), or (2) after polyurethane formation, but prior to
dispersing the polyurethane. The reaction between the neutralizing
agent and the potential anionic groups may be conducted between
about 20.degree. C. and about 150.degree. C., but is normally
conducted at temperatures below about 100.degree. C., optionally
between about 30.degree. C. and about 80.degree. C., and more
specifically between about 50.degree. C. and about 70.degree. C.,
with agitation of the reaction mixture. The ionic or potentially
ionic group may be used in amount of about 2 to about 20 percent by
weight solids.
Other Isocyanate-Reactive Components
[0127] In addition to the diols Z.sub.1 and Z.sub.2 other diols may
be included in the urea terminated polyurethane dispersant. These
diols contain at least two hydroxyl groups, and optionally have a
molecular weight of from about 60 to about 6000. The molecular
weights can be determined by hydroxyl group analysis (OH
number).
[0128] Examples of polymeric polyols include polyethers,
polyacetals, polyester amides, polythioethers and mixed polymers. A
combination of these polymers can also be used.
[0129] Suitable polyether polyols are obtained in a known manner by
the reaction of starting compounds that contain reactive hydrogen
atoms with alkylene oxides such as ethylene oxide, propylene oxide,
butylene oxide, styrene oxide, tetrahydrofuran, epichlorohydrin or
mixtures of these.
[0130] Polyethers that have been obtained by the reaction of
starting compounds containing amine compounds can also be used.
Examples of these polyethers as well as suitable polyhydroxy
polyacetals, polyhydroxy polyacrylates, polyhydroxy polyester
amides, polyhydroxy polyamides and polyhydroxy polythioethers, are
disclosed in U.S. Pat. No. 4,701,480.
[0131] These additional diol components will lead to a polyurethane
with different R.sub.2 components. Depending on the sequence of
addition the distribution of the various diol, R.sub.2 components
can be random or in blocks, depending on the sequence of addition
during the synthesis of the polyurethane.
[0132] Possible other diols and polyether diols include those shown
in Structure IV can either be based on alpha,omega dialcohol (p=1)
with at least 3 methylene groups (m=3) and less than or equal to 30
methylene groups or a polyether diol (p greater than 1).
##STR00006##
p is greater than or equal to 1, when p is 1, q greater than or
equal to 3 to about 30, when p is 2 or greater, q greater than or
equal to 3 to about 12; R.sub.7, R.sub.8 each is independently
selected from the group consisting of hydrogen, alkyl, substituted
alkyl, and aryl; where the R7 is the same or different for each
substituted methylene group where R.sub.7 and R.sub.7 or R.sub.8
can be joined to form a cyclic structure.
[0133] The additional polyether diol shown in Structure (IV) {where
p greater than 1} are oligomers and polymers in which at least 50%
of the repeating units have 3 to 12 methylene groups in the ether
chemical groups.
[0134] For p=2 or greater and q=3 the polyether diol is derived
from 1,3-propanediol. The employed PO3G may be obtained by any of
the various well known chemical routes or by biochemical
transformation routes. The 1,3-propanediol may be obtained
biochemically from a renewable source ("biologically-derived"
1,3-propanediol). The description of this biochemically obtained
1,3-propanediol can be found in co owned filed US Patent
Application, US20080039582). This polyether diol for use in the
urea terminated polyurethane may have a number average molecular
weight (M.sub.n) in the range of about 200 to about 5000, and more
preferably from about 240 to about 3600. Blends of this polyether
diol shown in Structure (V) can also be used. For example, the
polyether diol shown in Structure (V) can comprise a blend of a
higher and a lower molecular weight. For instance mixtures of
Structure (V) can have a number average molecular weight of from
about 1000 to about 5000, and another diol of Structure (V) can
have a number average molecular weight of from about 200 to about
750. The M.sub.n of the blended, polyether diol shown in Structure
(V) will preferably still be in the range of from about 250 to
about 3600.
Pigments
[0135] A wide variety of organic and inorganic pigments, alone or
in combination, may be dispersed with the urea terminated
polyurethane dispersant to prepare an ink, especially an inkjet
ink. The term "pigment" as used herein means an insoluble colorant
that requires it to be dispersed with a dispersant and processed
under dispersive conditions with the dispersant present. The
insoluble colorant includes pigments and disperse dyes. The
dispersion process results in a stable dispersed pigment. The
pigment used with the inventive urea terminated polyurethane
dispersants does not include self-dispersed pigments. The pigment
particles are sufficiently small to permit free flow of the ink
through the ink jet printing device, especially at the ejecting
nozzles that usually have a diameter ranging from about 10 micron
to about 50 micron. The particle size also has an influence on the
pigment dispersion stability, which is critical throughout the life
of the ink. Brownian motion of minute particles will help prevent
the particles from flocculation. It is also desirable to use small
particles for maximum color strength and gloss. The range of useful
particle size is typically about 0.005 micron to about 15 micron.
Preferably, the pigment particle size should range from about 0.005
to about 5 micron and, most preferably, from about 0.005 to about 1
micron. The average particle size as measured by dynamic light
scattering is less than about 500 nm, preferably less than about
300 nm.
[0136] The selected pigment(s) may be used in dry or wet form. For
example, pigments are usually manufactured in aqueous media and the
resulting pigment is obtained as water-wet presscake. In presscake
form, the pigment is not agglomerated to the extent that it is in
dry form. Thus, pigments in water-wet presscake form do not require
as much deflocculation in the process of preparing the inks as
pigments in dry form. Representative commercial dry pigments are
listed in U.S. Pat. No. 5,085,698.
[0137] In the case of organic pigments, the ink may contain up to
approximately 30%, optionally about 0.1 to about 25%, and more
specifically from about 0.25 to about 10%, pigment by weight based
on the total ink weight. If an inorganic pigment is selected, the
ink will tend to contain higher weight percentages of pigment than
with comparable inks employing organic pigment, and may be as high
as about 75% in some cases, since inorganic pigments generally have
higher specific gravities than organic pigments.
[0138] The urea terminated polyurethane polymer dispersant is
present in the range of about 0.1 to about 20%, optionally in the
range of about 0.2 to about 10%, by weight based on the weight of
the total ink composition.
[0139] When the ionic content is low, less than about 90 meq per
100 g of polyurethane, the urea terminated polyurethane dispersant
have a low salt stability. This low salt stability is associated
with the phenomena that the pigment in the inkjet ink will crash
out onto the surface of a substrate, especially paper and produce a
high optical density. The optical density is similar to what has
been obtained with self-dispersed pigments like those described in
U.S. Pat. No. 6,852,156.
[0140] A characteristic of a dispersion with low salt stability is
that when it is tested with salt solutions the urea terminated
polyurethane dispersed pigment will come out of solution as
described in US2005/00905099.
[0141] Unexpectedly, the urea terminated polyurethane dispersed
pigment when they have a ionic content of less than about 90 meq
per 100 g of polyurethane gives the improved optical density
relative to pigment with acrylic and acrylate-based dispersants,
but also give improved Distinctness of Image (DOI).
Polyurethane and Polyurethane Dispersion Preparation
[0142] The process of preparing the polyurethane dispersants of the
invention begins with preparation of the polyurethane, which can be
prepared by mixture or stepwise methods. The physical form of the
polyurethane prior to its use as a dispersant is as a dispersion.
In the mixture process, isocyanate terminated polyurethane is
prepared by mixing the polyol of Structure (II), the ionic
reactant, up to 50% other diols, and solvent, and then adding
diisocyanate to the mixture. This reaction is conducted at from
about 40.degree. C. to about 100.degree. C., and optionally from
about 50.degree. C. to about 90.degree. C. The ratio of isocyanate
to isocyanate reactive groups is from about 1.3:1 to about 1.05:1,
and more optionally from about 1.25:1 to about 1.1:1. When the
targeted percent isocyanate is reached, then the primary or
secondary amine chain terminator is added, and then base or acid is
added to neutralize ionizable moieties incorporated from the
ionizable reagent. The polyurethane solution is then converted to
an aqueous polyurethane dispersion via the addition of water under
high shear. If present, the volatile solvent is distilled under
reduced pressure.
[0143] The NCO-functional prepolymers should be substantially
linear, and this may be achieved by maintaining the average
functionality of the prepolymer starting components at or below
2:1.
[0144] In some cases, addition of neutralization agent, preferably
tertiary amines, may be beneficially added during early stages of
the polyurethane synthesis. Alternately, advantages may be achieved
via the addition of the neutralization agent, as the alkali base or
an amine, simultaneously along with the water of inversion at high
shear.
[0145] In the stepwise method, isocyanate terminated polyurethane
is prepared by dissolving the ionic reactant in solvent, and then
adding diisocyanate to the mixture. Once the initial percent
isocyanate target is reached, the polyol component is added. This
reaction is conducted at from about 40.degree. C. to about
100.degree. C., and optionally from about 50.degree. C. to about
90.degree. C. The preferred ratio of isocyanate to isocyanate
reactive groups is from about 1.3:1 to about 1.05:1, and more
preferably from about 1.25:1 to about 1.1:1. Alternately, the diols
and/or polyether polyols and up to 50% other diols may be reacted
in the first step, and the ionic reactant may be added after the
initial percent isocyanate target is reached. When the final
targeted percent isocyanate is reached, then the chain terminator
is added, and then base or acid is added to neutralize ionizable
moieties incorporated from the ionizable reagent. The polyurethane
solution is then converted to an aqueous polyurethane dispersion
via the addition of water under high shear. If present, the
volatile solvent is distilled under reduced pressure.
[0146] In all polyurethane reaction schemes if the neutralization
reactant has isocyanate reaction capability, (for example an
alcohol, primary amine or secondary amine) it cannot be added prior
to the chain terminating, urea forming amine. If the neutralization
agent can function as a chain terminating reactant according to
Structure (I), then it must be added after all of the other
isocyanate reactive groups have been reacted.
[0147] Catalysts are not necessary to prepare the polyurethanes,
but may provide advantages in their manufacture. The catalysts most
widely used are tertiary amines and organo-tin compounds such as
stannous octoate, dibutyltin dioctoate, dibutyltin dilaurate.
[0148] Preparation of the Polyurethane for Subsequent Conversion to
a dispersion is facilitated by using solvent. Suitable solvents are
those that are miscible with water and inert to isocyanates and
other reactants utilized in forming the polyurethanes. If it is
desired to prepare a solvent-free dispersion, then the solvent used
should have sufficient volatility to allow removal by distillation.
Typical solvents useful in the practice of the invention are
acetone, methyl ethyl ketone, toluene, and N-methyl pyrollidone.
Alternatively, the polyurethane can be prepared in a melt with less
than 5% solvent.
[0149] The polyurethane can be usually prepared by a multiple step
process. Typically, in the first stage, a diisocyanate is reacted
with a compound, polymer, or mixtures of compounds, mixture of
polymers or a mixture thereof, each containing two NCO-reactive
groups, to form a prepolymer. An additional compound or compounds,
all containing .gtoreq.2 NCO-reactive groups as well as a
stabilizing ionic functionality, is also used to form an
intermediate polymer. This intermediate polymer or pre-polymer can
be terminated with either an NCO-group or a NCO-reactive group. The
terminal groups are defined by the molar ratio of NCO to
NCO-reactive groups in the prepolymer stage. Typically, the
pre-polymer is an NCO-terminated material that is achieved by using
a molar excess of NCO. Thus, the molar ratio of diisocyanate to
compounds containing two isocyanate-reactive groups is greater than
1.0:1.0, optionally greater than about 1.05:1.0 and even greater
than about 1.1:1.0. In general, the ratios are achieved by
preparing, in a first stage, an NCO-terminated intermediate by
reacting one of the NCO-reactive compounds, having at least 2 NCO
reactive groups, with all or part of the diisocyanate. This is
followed, in sequence, by additions of other NCO-reactive
compounds, if desired. When all reactions are complete the group,
NCO and/or NCO-reactive groups will be found at the termini of the
pre-polymer. These components are reacted in amounts sufficient to
provide a molar ratio such that the overall equivalent ratio of NCO
groups to NCO-reactive groups is achieved and the targeted urea
content is obtained.
[0150] Process conditions for preparing the NCO containing
prepolymers have been discussed in the publications previously
noted. The finished NCO-containing prepolymer should have a
isocyanate content of about 1 to about 20%, optionally about 1 to
about 10% by weight, based on the weight of prepolymer solids.
[0151] Mixtures of compounds and/or polymers having mixed NCO
reactive groups are also possible.
[0152] In order to have a stable dispersion, a sufficient amount of
the ionic groups (if present) must be neutralized so that, the
resulting polyurethane will remain stably dispersed in the aqueous
medium. Generally, at least about 70%, preferably at least about
80%, of the carboxylic acid groups are neutralized to the
corresponding carboxylate salt groups. Alternatively, cationic
groups in the polyurethane can be quaternary ammonium groups
(--NR.sub.3Y, wherein Y is a monovalent anion such as chlorine or
hydroxyl).
[0153] Suitable neutralizing agents for converting the acid groups
to salt groups include tertiary amines, alkali metal cations and
ammonia. Neutralizing agents can be the trialkyl-substituted
tertiary amines, such as triethyl amine, tripropyl amine,
dimethylcyclohexyl amine, dimethylethanol amine, and triethanol
amine and dimethylethyl amine. Substituted amines are also useful
neutralizing groups such as diethyl ethanol amine or diethanol
methyl amine.
[0154] Neutralization may take place at any point in the process.
Typical procedures include at least some neutralization of the
prepolymer, which is then chain extended/terminated in water in the
presence of additional neutralizing agent.
[0155] Conversion to the aqueous dispersion is completed by
addition of water. If desired, solvent can then be removed
partially or substantially by distillation under reduced pressure.
The final product is a stable, aqueous polyurethane dispersion
having a solids content of up to about 60% by weight, preferably
from about 10% to about 60% by weight, and more preferably from
about 20% to about 45% by weight. However, it is always possible to
dilute the dispersions to any minimum solids content desired. The
solids content of the resulting dispersion may be determined by
drying the sample in an oven at 150.degree. C. for 2 hours and
comparing the weights before and after drying. The particle size is
generally below about 1.0 micron, and preferably between about 0.01
to about 0.5 micron. The average particle size should be less than
about 0.5 micron, and preferably between about 0.01 to about 0.3
micron. The small particle size enhances the stability of the
dispersed particles
[0156] In accordance with the present invention the term "aqueous
polyurethane dispersion" refers to aqueous dispersions of polymers
containing urethane groups, as that term is understood by those of
ordinary skill in the art. These polymers also incorporate
hydrophilic functionality to the extent required to maintain a
stable dispersion of the polymer in water. The compositions of the
invention are aqueous dispersions that comprise a continuous phase
comprising water, and a dispersed phase comprising
polyurethane.
[0157] Fillers, plasticizers, pigments, carbon black, silica sols,
other polymer dispersions and the known leveling agents, wetting
agents, antifoaming agents, stabilizers, and other additives known
for the desired end use, may also be incorporated into the
dispersions.
Polyurethane Pigment Dispersion Preparation
[0158] The urea-terminated polyurethanes are dispersants for
particles, such as pigments. In this case, the polyurethane is
either 1.) utilized as a dissolved polyurethane in a compatible
solvent where the initial polyurethane/particle mixture is prepared
and then processed using dispersion equipment to produce the
aqueous polyurethane dispersed particle; or 2) the polyurethane
dispersion and the particle dispersed are mixed in a compatible
solvent system which, in turn is processed using dispersion
equipment to produce the aqueous polyurethane dispersed particle.
While not being bound by theory, it is assumed that the particle
and the polyurethane have the appropriate physical/chemical
interactions that are required for a stable dispersion.
Furthermore, it is possible that some of the polyurethane is not
bound to the pigment and exists either as a dispersion of the
polyurethane or polyurethane dissolved in the liquid phase of the
dispersion.
[0159] The urea terminated polyurethane and ink compositions of the
invention may be prepared by methods known in the art. It is
generally desirable to make the urea terminated polyurethane in a
concentrated form, which is subsequently diluted with a suitable
liquid containing the desired additives. The urea terminated
polyurethane dispersion is first prepared by premixing the selected
pigment(s) and urea terminated polyurethane polymeric dispersant(s)
in an aqueous carrier medium (such as water and, optionally, a
water-miscible solvent), and then dispersing or deflocculating the
pigment. The dispersing step may be accomplished in a 2-roll mill,
media mill, a horizontal mini mill, a ball mill, an attritor, or by
passing the mixture through a plurality of nozzles within a liquid
jet interaction chamber at a liquid pressure of at least 5,000 psi
to produce a uniform dispersion of the pigment particles in the
aqueous carrier medium (microfluidizer). Alternatively, the
concentrates may be prepared by dry milling the polymeric
dispersant and the pigment under pressure. The media for the media
mill is chosen from commonly available media, including zirconia,
YTZ, and nylon. These various dispersion processes are in a general
sense well-known in the art, as exemplified by, U.S. Pat. No.
5,022,592, U.S. Pat. No. 5,026,427, U.S. Pat. No. 5,310,778, U.S.
Pat. No. 5,891,231, U.S. Pat. No. 5,679,138, U.S. Pat. No.
5,976,232 and US20030089277. Routinely used milling processes
include the -roll mill, media mill, and by passing the mixture
through a plurality of nozzles within a liquid jet interaction
chamber at a liquid pressure of at least 5,000 psi.
[0160] After the milling process is complete the pigment
concentrate may be "let down" into an aqueous system. "Let down"
refers to the dilution of the concentrate with mixing or
dispersing, the intensity of the mixing/dispersing normally being
determined by trial and error using routine methodology, and often
being dependent on the combination of the polymeric dispersant,
solvent and pigment. The determination of sufficient let down
conditions is needed for all combinations of the polymeric
dispersant, the solvent and the pigment.
[0161] After the urea terminated polyurethane dispersion
preparation, the amount of water-miscible solvent may be more than
some ink jet applications will tolerate. For some of the urea
terminated polyurethane dispersions, it thus may be necessary to
ultrafilter the final dispersion to reduce the amount of
water-miscible solvent. To improve stability and reduce the
viscosity of the pigment dispersion, it may be heat treated by
heating from about 30.degree. C. to about 100.degree. C., with an
optional temperature being about 70.degree. C. for about 10 to
about 24 hours. Longer heating does not affect the performance of
the dispersion.
[0162] The amount of polymeric urea terminated polyurethane
dispersants required to stabilize the pigment is dependent upon the
specific urea terminated polyurethane dispersants, the pigment and
vehicle interaction. The weight ratio of pigment to polymeric urea
terminated polyurethane dispersants will typically range from about
0.5 to about 6. An optional range is about 0.75 to about 4.
[0163] While not being bound by theory, it is believed that the
urea terminated polyurethane's provide improved ink properties by
the following means. Stable aqueous dispersions are critical for
inkjet inks to assure long-lived ink cartridges and few problems
with failed nozzles, etc. It is, however, desirable for the ink to
become unstable as it is jetted onto the media so that the pigment
in the ink "crashes out" onto the surface of the media (as opposed
to being absorbed into the media). With the pigment on the surface
of the media, beneficial properties of the ink can be obtained.
[0164] The urea terminated polyurethane polymeric dispersants
provide novel dispersants that sufficiently stabilize the ink prior
to jetting (such as in the cartridge) but, as the ink is jetted
onto the paper, the pigment system is destabilized and the pigment
remains on the surface of the media. This leads to improved ink
properties.
EXAMPLES
[0165] The following examples are presented for the purpose of
illustrating the invention and are not intended to be limiting. All
parts, percentages, etc., are by weight unless otherwise
indicated.
[0166] The dispersions whose preparation is described in the
examples below were characterized in terms of their particle size
and particle size distribution.
Extent of Polyurethane Reaction
[0167] The extent of polyurethane reaction was determined by
detecting NCO % by dibutylamine titration, a common method in
urethane chemistry.
[0168] In this method, a sample of the NCO containing prepolymer is
reacted with a known amount of dibutylamine solution and the
residual amine is back titrated with HCl.
Particle Size Measurements
[0169] The particle size for the polyurethane dispersions, pigments
and the inks were determined by dynamic light scattering using a
Microtrac.RTM. UPA 150 analyzer from Honeywell/Microtrac
(Montgomeryville Pa.).
[0170] This technique is based on the relationship between the
velocity distribution of the particles and the particle size. Laser
generated light is scattered from each particle and is Doppler
shifted by the particle Brownian motion. The frequency difference
between the shifted light and the unshifted light is amplified,
digitalized and analyzed to recover the particle size
distribution.
[0171] The reported numbers below are the volume average particle
size.
Solid Content Measurement
[0172] Solid content for the solvent free polyurethane dispersions
was measured with a moisture analyzer, model MA50 from Sartorius.
For polyurethane dispersions containing high boiling solvent, such
as NMP, tetraethylene glycol dimethyl ether, the solid content was
then determined by the weight differences before and after baking
in 150.degree. C. oven for 180 minutes
Urea Terminated Polyurethane Dispersant Example 1
IPDI/Pripol 2033/DEA/KOH AN40
[0173] To a dry, alkali- and acid-free flask, equipped with an
addition funnel, a condenser, stirrer and a nitrogen gas line was
added 155 g Pripol 2033, a hydrocarbon diol from Uniqema, 30 g DMPA
and 93 g Tetraglyme. The contents were heated to 60.degree. C. and
mixed well. 122 g IPDI was then added to the flask via the addition
funnel at 60.degree. C. over 60 min, with any residual IPDI being
rinsed from the addition funnel into the flask with 10 g
Tetraglyme.
[0174] The flask temperature was raised to 80.degree. C., held for
120 minutes until NCO % was 1.05% or less, then 10.8 gram DEA was
added over 5 minutes.
[0175] With the temperature at 80.degree. C., mixture of 26.5 gram
45% KOH solution and 784 g deionized (DI) water was added over 10
minutes via the addition funnel, which was then rinsed with 30.0 g
water. The mixture was held at 50.degree. C. for 1 hr, then cooled
to room temperature. The final polyurethane dispersion had a
viscosity of 55 cPs, 21% solids, pH 7.580, particle size of d50=132
nm.
Urea Terminated Polyurethane Dispersant Example 2
IPDI/XP2501/DEA/TEA AN60
[0176] To a dry, alkali- and acid-free flask, equipped with an
addition funnel, a condenser, stirrer and a nitrogen gas line was
added 140 g Desmophen XP2501, a 1000 MW polycarbonate/ester diol
from Bayer, 47 g DMPA, 31.6 g TEA, 97 g acetone and 0.06 g DBTL.
The contents were heated to 40.degree. C. and mixed well. 136 g
IPDI was then added to the flask via the addition funnel at
40.degree. C. over 60 min, with any residual IPDI being rinsed from
the addition funnel into the flask with 10 g acetone.
[0177] The flask temperature was raised to 50.degree. C., held at
50.degree. C. until NCO % was 2.2% or less, then 24.3 gram DEA was
added over 5 minutes followed by 5 gram acetone rinse. After 1 hour
at 50.degree. C., 600 g deionized (DI) water was added over 10
minutes via the addition funnel. The mixture was held at 50.degree.
C. for 1 hr, then cooled to room temperature.
[0178] Acetone (-102 g) was removed under vacuum, leaving a
polyurethane solution with about 35.0% solids by weight. The final
polyurethane dispersion had a viscosity of 97 cPs, pH 6.8, particle
size of d50=8 nm.
Urea Terminated Polyurethane Dispersant Example 3
IPDI/Stepanol PS2352/DEA/TEA AN60
[0179] To a dry, alkali- and acid-free flask, equipped with an
addition funnel, a condenser, stirrer and a nitrogen gas line was
added 100 g Stepanol PS2352, a 500 MW polydiethylene glycol
orthorphathlate diol from Stepan, 41 g DMPA, 27.5 g TEA, 84 g
acetone and 0.06 g DBTL. The contents were heated to 40.degree. C.
and mixed well. 141.5 g IPDI was then added to the flask via the
addition funnel at 40.degree. C. over 60 min, with any residual
IPDI being rinsed from the addition funnel into the flask with 10 g
acetone.
[0180] The flask temperature was raised to 50.degree. C., held at
50.degree. C. until NCO % was 2.62% or less, then 25 gram DEA was
added over 5 minutes followed by 5 gram acetone rinse. After 1 hour
at 50.degree. C., 525 g deionized (DI) water was added over 10
minutes via the addition funnel. The mixture was held at 50.degree.
C. for 1 hr, then cooled to room temperature.
[0181] Acetone (-99 g) was removed under vacuum, leaving a
polyurethane solution with about 33.0% solids by weight. The final
polyurethane dispersion had a viscosity of 500 cPs, pH 8.13,
particle size of d50=44 nm.
Comparative Polyurethane 1
DEA Terminated 1,6 Hexane Diol, AN60
[0182] To a dry, alkali- and acid-free flask, equipped with an
addition funnel, a condenser, stirrer and a nitrogen gas line was
added 55 g 1,6 Hexanediol, 48 g DMPA, 32.2 g TEA, 100 g acetone and
0.06 g DBTL. The contents were heated to 40.degree. C. and mixed
well. 227 g IPDI was then added to the flask via the addition
funnel at 40.degree. C. over 60 min, with any residual IPDI being
rinsed from the addition funnel into the flask with 10 g
acetone.
[0183] The flask temperature was raised to 50.degree. C., held at
50.degree. C. until NCO % was 3.5% or less, then 39.5 gram DEA was
added over 5 minutes followed by 5 gram acetone rinse. After 1 hour
at 50.degree. C., 613 g deionized (DI) water was added over 10
minutes via the addition funnel. The mixture was held at 50.degree.
C. for 1 hr, then cooled to room temperature.
[0184] Acetone (-115 g) was removed under vacuum, leaving a
polyurethane solution with about 35.0% solids by weight. The final
polyurethane dispersion had a viscosity of 30 cPs, pH 7.5, particle
size of d50=86.5 nm.
Comparative Polyurethane 2
T650/DMBA/DEA, AN40
[0185] To a dry, alkali- and acid-free flask, equipped with an
addition funnel, a condenser, stirrer and a nitrogen gas line was
added 125 g Terathane 650, a 650 MW polyether diol from Invista, 25
g DMBA, and 0.04 g DBTL. The contents were heated to 90.degree. C.
and mixed well. 110 g TMXDI was then added to the flask via the
addition funnel at 90.degree. C. over 60 min. The flask temperature
was raised to 95.degree. C., held at 95.degree. C. until NCO % was
2.9% or less, then 17.8 gram DEA was added over 5 minutes. After 1
hour at 95.degree. C., the flask temperature was lowered to
75.degree. C. 15.4 gram TEA was then added followed by 465 g
deionized (DI) water over 10 minutes via the addition funnel. The
mixture was held at 75.degree. C. for 1 hr, then cooled to room
temperature.
[0186] The final polyurethane dispersion had a viscosity of 40 cPs,
37.6% solids, pH 7.9, particle size of d50=14.5 nm.
Comparative Polyurethane 3
T650/TMXDI/DMBA/Aminoacid/DEA, AN 40
[0187] To a dry, alkali- and acid-free flask, equipped with an
addition funnel, a condenser, stirrer and a nitrogen gas line was
added 155 g Terathane 650, a 650 MW polyether diol from Invista, 18
g DMBA, and 0.04 g DBTL. The contents were heated to 90.degree. C.
and mixed well. 110 g TMXDI was then added to the flask via the
addition funnel at 90.degree. C. over 60 min. The flask temperature
was raised to 95.degree. C., held at 95.degree. C. for 1 hour, then
8 gram DEA was added over 5 minutes and held at 95.degree. C. until
NCO % was 1.5% or lower. The flask temperature was lowered to
75.degree. C. 11.55 TEA was added and mixed well. 325 g deionized
(DI) water was added over 10 minutes via the addition funnel
followed by mixture of 6-aminocaproic acid (13.6 g), TEA (9.4 g)
and water (130 g) solution. The dispersion was held at 75.degree.
C. for 1 hr, then cooled to room temperature.
[0188] The final polyurethane dispersion had a viscosity of 40 cPs,
28% solids, pH 10, particle size of d50=18.5 nm.
Comparative Polyurethane 4
IPDI/T650/DEA/KOH AN60
[0189] To a dry, alkali- and acid-free flask, equipped with an
addition funnel, a condenser, stirrer and a nitrogen gas line was
added 115 g Terathane 650, a 650 MW polyether diol from Invista, 39
g DMPA and 115 g Tetraglyme. The contents were heated to 60.degree.
C. and mixed well. 115 g IPDI was then added to the flask via the
addition funnel at 60.degree. C. over 60 min, with any residual
IPDI being rinsed from the addition funnel into the flask with 10 g
Tetraglyme.
[0190] The flask temperature was raised to 80.degree. C., held for
120 minutes until NCO % was 1.17% or less, then 10.5 gram DEA was
added over 5 minutes.
[0191] With the temperature at 80.degree. C., mixture of 34.4 gram
45% KOH solution and 754.5 g deionized (DI) water was added over 10
minutes via the addition funnel. The mixture was held at 50.degree.
C. for 1 hr, then cooled to room temperature. The final
polyurethane dispersion had a viscosity of 18.5 cPs, 24% solids, pH
7.42, particle size of d50=4.4 nm.
Comparative Polyurethane Dispersant 5 with Diamine as Chain
Extender
[0192] To a dry, alkali- and acid-free flask, equipped with an
addition funnel, a condenser, stirrer and a nitrogen gas line was
added 699.2 g Desmophen C 1200, a polyester carbonate diol,
(Bayer), 280.0 g acetone and 0.06 g DBTL. The contents were heated
to 40.degree. C. and mixed well. 189.14 g IPDI was then added to
the flask via the addition funnel at 40.degree. C. over 60 min,
with any residual IPDI being rinsed from the addition funnel into
the flask with 15.5 g acetone.
[0193] The flask temperature was raised to 50.degree. C., held for
30 minutes then followed by 44.57 g DMPA, then followed by 25.2 g
TEA, was added to the flask via the addition funnel, which was then
rinsed with 15.5 g acetone. The flask temperature was then raised
again to 50.degree. C. and held at 50.degree. C. until NCO % was
1.14% or less.
[0194] With the temperature at 50.degree. C., 1520.0 g deionized
(DI) water was added over 10 minutes, followed by 131.00 g EDA (as
a 6.25% solution in water) over 5 minutes, via the addition funnel,
which was then rinsed with 80.0 g water. The mixture was held at
50.degree. C. for 1 hr, then cooled to room temperature.
[0195] Acetone (-310.0 g) was removed under vacuum, leaving a final
dispersion of polyurethane with about 35.0% solids by weight.
Preparation of Pigmented Dispersions
[0196] Pigmented dispersions were prepared with magenta, yellow,
cyan and black pigments. For the examples in Table 1, the following
pigments were used Clarient Hostaperm Pink E-02, PR-122 (Magenta),
and Degussa's Nipex 180 IQ powder (Black, K).
[0197] The following procedure was used to prepare the pigment
dispersions with invention dispersing resin. Using an Eiger
Minimill, the premix was prepared at typically 20-30% pigment
loading and the targeted dispersant level was selected at a P/D
(pigment/dispersant) ratio of 1.5-3.0. A P/D of 2.5 corresponds to
a 40% dispersant level on pigment. Optionally, a co-solvent was
added at 10% of the total dispersion formulation to facilitate
pigment wetting and dissolution of the resins in premix stage and
ease of grinding during milling stage. Although other similar
co-solvents are suitable, triethylene glycol monobutyl ether (TEB
as supplied from Dow Chemical) was the co-solvent of choice. The
invention resins were pre-neutralized with either KOH or amine to
facilitate solubility and dissolution into water. During the premix
stage the pigment level was maintained at typically 27% and was
subsequently reduced to about 24% during the milling stage by
adding deionized water for optimal media mill grinding conditions.
After completion of the milling stage, which was typically 4 hours,
the remaining letdown of de-ionized water was added and thoroughly
mixed.
[0198] All the pigmented dispersions processed with co-solvent were
purified using an ultrafiltration process to remove co-solvent(s)
and filter out other impurities and ions that may be present. After
completion, the pigment levels in the dispersions were reduced to
about 10 to 15%. A total of 6 different magenta and 3 black
dispersions were prepared with the invention dispersing resins,
which are shown in Table 1 below.
Example Pigment Dispersions
[0199] Tabulated below are pigment dispersions stabilized with
polyurethane dispersants, synthesized by the method previously
outlined above. The polyurethane dispersants listed refer to the
Polyurethane Dispersants listed above.
[0200] The initial dispersion properties are tabulated and their
one-week oven stability results are reported in Table 1 and 2,
respectively. The initial particle size, viscosity, and
conductivity for these dispersions were 98-142 nm, 3.7-4.8 cPs,
respectively, with the pH ranging from 6.4 to 6.8. The particle
size for the Inv Ink dispersion was stable with oven aging with
only minimal changes in particle size, viscosity and pH.
TABLE-US-00001 TABLE 1 Pigments Dispersion Example Particle
Polyurethane Size Pigment Pig. Pigment/ Dispersant D50, Viscosity
Dispersion % Dispersant Example nm (cPs) pH Inv 11.7 2.5 1 98 4.5
8.6 Dispersion M1 Inv 15.2 2.5 2 142 4.8 6.4 Dispersion K2 Inv 15
2.5 3 83 3.7 6.6 Dispersion K3 Comp M1 12.6 2.5 Comp pud 2 102 5.9
8.5 Comp M2 12.5 2.5 Comp pud 3 95 5.9 8.8 Comp. M3 2.5 Comp. NA
Gelled NA PUD 5 Comp K1 14.7 2.5 Comp 98 3.6 6.8 PUD 1 Comp K2 15.1
2.5 Comp 105 4.8 7.1 PUD 4
[0201] In addition, a dispersion Comparative Dispersion
Magenta--was made from the Comparative polyurethane Dispersant 5, a
diamine chain extended polyurethane dispersion. This disperant
failed as a dispersant for the magenta pigment; it gelled at the
pre-mix stage of the dispersion process.
TABLE-US-00002 TABLE 2 Pigment Dispersion Properties after Oven
Aging (70.degree. C. 1 week) Particle Pigment Size Viscosity
Dispersion nm, d.sub.50 (cPs) pH Inv 97 3.1 9.0 Dispersion M1 COMP
M1 95 4.0 8.4 COMPM2 120 5.3 8.9 Comp K1 130 12 7.0 Comp K2 117 6.7
7.0
Preparation of Inks
[0202] The inks were prepared with pigmented dispersions made using
invention-dispersing polymers described above, by conventional
process known to the art. The pigmented dispersions are processed
by routine operations suitable for inkjet ink formulation.
[0203] Typically, in preparing ink, all ingredients except the
pigmented dispersion are first mixed together. After all the other
ingredients are mixed, the pigmented dispersion is added. Common
ingredients in ink formulations useful in pigmented dispersions
include one or more humectants, co-solvent(s), one or more
surfactants, a biocide, a pH adjuster, and de-ionized water.
[0204] The selected magenta and black pigmented dispersions from
example dispersions in Table 1 were prepared into Magenta ink
formulations in which the targeted percent pigment in ink jet ink
was 4.0%. Water, Polyurethane binder, Dowanol TPM, 1,2-hexanediol,
ethylene glycol, Surfynol 445, and Proxel GXL were mixed with the
prepared pigment dispersions in the percentages detailed in Table
3. Polyurethane binder is a crosslinked polyurethane dispersion
prepared as PUD EXP1 in US 20050215663 A1, Dowanol TPM is
Tripropylene glycol methyl ether from Dow Chemical, Proxel GXL is a
biocide available from Avecia, Inc. and Surfynol 440 is a
surfactant available from Air Products. The inks were mixed for 4
hours and then filtered through a 1 micron filtration apparatus,
removing any large agglomerates, aggregates or particulates.
TABLE-US-00003 TABLE 3 Ink Composition Weight % in Ink Ingredient
Ink 1,2 hexanediol 7.00% Dowanol TPM 2.60% Ethylene glycol 6.3%
Surfynol 440 0.25% Proxel GXL 0.15% Polyurethane binder 4.00%
Pigment 4.00% Water (Balance to balance 100%)
Ink Properties
[0205] The ink properties measured were pH, viscosity,
conductivity, particle size and surface tension. The particle size
was measured using a Leeds and Northrup, Microtrac Ultrafine
Particle Analyser (UPA). The viscosity was measured with a
Brookfield Viscometer (Spindle 00, 25.degree. C., 60 rpm). The
properties of the inks prepared using example dispersions
containing invention dispersing resins are reported in Table 4.
[0206] Jet velocity, drop size and stability are greatly affected
by the surface tension and the viscosity of the ink. Inkjet inks
typically have a surface tension in the range of about 20 dyne/cm
to about 60 dyne/cm at 25.degree. C. Viscosity can be as high as 30
cPs at 25.degree. C., but is typically significantly lower. The
inks have physical properties compatible with a wide range of
ejecting conditions, i.e., driving frequency of the piezo element,
or ejection conditions for a thermal head, for either a
drop-on-demand device or a continuous device, and the shape and
size of the nozzle. The inks of this invention should have
excellent storage stability for long periods so as not clog to a
significant extent in an ink jet apparatus. Further, it should not
alter the materials of construction of the ink jet printing device
it comes in contact with, and be essentially odorless and
non-toxic.
[0207] Although not restricted to any particular viscosity range or
printhead, the inventive inks are suited to lower viscosity
applications such as those required by higher resolution (higher
dpi) printheads that jet small droplet volumes, e.g. less than
about 20 pL. Thus the viscosity (at 25.degree. C.) of the inventive
inks can be less than about 10 cPs, is preferably less than about 7
cPs, and most advantageously is less than about 5 cPs.
TABLE-US-00004 TABLE 4 Ink Properties of Pigmented Inks using
Polyurethane Dispersants Particle Surface Conductivity Viscosity
Size Tension Ink pH (.mu.s/cm) (cPs) d.sub.50 Dynes/cm Ink-M1 8.0
0.54 3.5 112 29.6 Ink-K3 8.0 0.90 4.2 100 30 Comp 8.2 0.41 5.7 190
29.4 Ink-M1 Comp 8.0 0.41 9.3 185 29.6 Ink-M2
Printing Properties
[0208] The Inkjet inks with invention dispersing resins were
printed using a commercially available Epson 3000 piezo printhead
type printer although any suitable inkjet printer could be used.
The substrate used was 419 100% cotton from Test fabrics. The
printed textiles may optionally be post processed with heat and/or
pressure, such as disclosed in US20030160851. In this case, all
test prints were fused at about 170.degree. C. for about 2
minutes.
[0209] Colorimetric measurements were done using a Minolta
Spectrophotometer CM-3600 d using Spectra Match software.
[0210] Where indicated the printed textile was tested for
washfastness according to methods developed by the American
Association of Textile Chemists and Colorists, (AATCC), Research
Triangle Park, N.C. The AATCC Test Method 61-1996, "Colorfastness
to Laundering, Home and Commercial: Accelerated", was used. In that
test, colorfastness is described as "the resistance of a material
to change in any of its color characteristics, to transfer of its
colorant(s) to adjacent materials or both as a result of the
exposure of the material to any environment that might be
encountered during the processing, testing, storage or use of the
material." Tests 3A was done and the color washfastness and stain
rating were recorded. The ratings for these tests are from 1-5 with
5 being the best result, that is, little or no loss of color and
little or no transfer of color to another material, respectively.
Crock measurements were made using methodology described in AATCC
Test Method 8-1996.
[0211] The printing results using an Epson 3000 piezo type printer,
for selective inks make with pigments stabilized by invention
dispersing resins are reported in Table 5.
TABLE-US-00005 TABLE 5 Print Properties of Pigmented Inks with
Polyurethane Dispersants 3A Ink OD washfastness Dry Crock Wet Crock
Ink-M1 1.04 4.5 3.0 3.0 Ink-K3 0.97 3.5 2.3 1.5 Comp Ink- 1.02 4.5
3.5 3.0 M1 Comp Ink- 1.02 4.0 3.5 3.0 M2
* * * * *